Bottom Line:
Here, we investigate the relative contributions of Vang, Fz and Dishevelled (Dsh), a membrane-associated protein acting downstream of Fz, in orienting SOP polarity.Genetic and live imaging analyses suggest that Dsh restricts the localization of a centrosome-attracting activity to the anterior cortex and that Vang is a target of Dsh in this process.Additionally, we find that the activity of Vang is dispensable for the non-autonomous polarizing activity of fz.

ABSTRACTDrosophila sensory organ precursor cells (SOPs) divide asymmetrically along the anterior-posterior (a-p) body axis to generate two different daughter cells. Planar Cell Polarity (PCP) regulates the a-p orientation of the SOP division. The localization of the PCP proteins Van Gogh (Vang) and Frizzled (Fz) define anterior and posterior apical membrane domains prior to SOP division. Here, we investigate the relative contributions of Vang, Fz and Dishevelled (Dsh), a membrane-associated protein acting downstream of Fz, in orienting SOP polarity. Genetic and live imaging analyses suggest that Dsh restricts the localization of a centrosome-attracting activity to the anterior cortex and that Vang is a target of Dsh in this process. Using a clone border assay, we provide evidence that the Vang and fz genes act redundantly in SOPs to orient its polarity axis in response to extrinsic local PCP cues. Additionally, we find that the activity of Vang is dispensable for the non-autonomous polarizing activity of fz. These observations indicate that both Vang and Fz act as cues for downstream effectors orienting the planar polarity axis of dividing SOPs.

pone-0004485-g004: Fz and Vang act redundantly.The orientation of SOP division was studied along the border of Vangstbm6c mutant clones generated in fz(RNAi) pupae (A–B′), of fz(RNAi) clones generated in Vangstbm6c mutant pupae (C–D′) and of Vangstbm6c mutant clones generated in dsh1 mutant pupae (E–F′). SOPs were identified using Sens (red) and orientation of the division was determined using Pins (blue). Clone borders were marked by nls-GFP (green). (A) fz(RNAi) Vangstbm6c SOP (GFP−) in Vangstbm6c mutant pupae. (B) Vangstbm6c mutant SOP (GFP+) at the border of fz(RNAi) Vangstbm6c mutant cells. (C) dsh1 Vangstbm6c SOP (GFP−) in dsh1 mutant pupae. (D) dsh1 mutant SOP (GFP+) at the border of dsh1 Vangstbm6c mutant cells. (E) fz(RNAi) Vangstbm6c SOP (GFP−) in fz(RNAi mutant pupae. (D) fz(RNAi) SOP (GFP+) at the border of fz(RNAi) Vangstbm6c mutant cells. Angle values corresponding to the genotypes studied in top panels are plotted in bottom panels as in Figure 3. Statistical differences were evaluated using Fisher exact test (4×2 contingency table). In all three genotypes, the orientation of SOPs located inside the clone (A′, C′ and E′) was not statistically different from the random distribution seen in wild-type control clones (see Fig. 3A′,B′). In contrast, the orientation of SOPs located outside the clone (B′, D′ and F′) was significantly different from the random distribution seen in wild-type control clones (see Fig. 3A′,B′). Additionally, no statistically significant differences were observed in the orientation of SOPs located either outside Vangstbm6c mutant clones in fz(RNAi) pupae (B′) or dsh1 mutant pupae (F′) and wild-type pupae (Fig. 3C′). Similarly, no statistically significant difference was observed in the orientation of SOPs located outside fz(RNAi) clones in Vangstbm6c mutant (D′) and wild-type pupae (Fig. 3E′).

pone-0004485-g004: Fz and Vang act redundantly.The orientation of SOP division was studied along the border of Vangstbm6c mutant clones generated in fz(RNAi) pupae (A–B′), of fz(RNAi) clones generated in Vangstbm6c mutant pupae (C–D′) and of Vangstbm6c mutant clones generated in dsh1 mutant pupae (E–F′). SOPs were identified using Sens (red) and orientation of the division was determined using Pins (blue). Clone borders were marked by nls-GFP (green). (A) fz(RNAi) Vangstbm6c SOP (GFP−) in Vangstbm6c mutant pupae. (B) Vangstbm6c mutant SOP (GFP+) at the border of fz(RNAi) Vangstbm6c mutant cells. (C) dsh1 Vangstbm6c SOP (GFP−) in dsh1 mutant pupae. (D) dsh1 mutant SOP (GFP+) at the border of dsh1 Vangstbm6c mutant cells. (E) fz(RNAi) Vangstbm6c SOP (GFP−) in fz(RNAi mutant pupae. (D) fz(RNAi) SOP (GFP+) at the border of fz(RNAi) Vangstbm6c mutant cells. Angle values corresponding to the genotypes studied in top panels are plotted in bottom panels as in Figure 3. Statistical differences were evaluated using Fisher exact test (4×2 contingency table). In all three genotypes, the orientation of SOPs located inside the clone (A′, C′ and E′) was not statistically different from the random distribution seen in wild-type control clones (see Fig. 3A′,B′). In contrast, the orientation of SOPs located outside the clone (B′, D′ and F′) was significantly different from the random distribution seen in wild-type control clones (see Fig. 3A′,B′). Additionally, no statistically significant differences were observed in the orientation of SOPs located either outside Vangstbm6c mutant clones in fz(RNAi) pupae (B′) or dsh1 mutant pupae (F′) and wild-type pupae (Fig. 3C′). Similarly, no statistically significant difference was observed in the orientation of SOPs located outside fz(RNAi) clones in Vangstbm6c mutant (D′) and wild-type pupae (Fig. 3E′).

Mentions:
Figure 4:

Bottom Line:
Here, we investigate the relative contributions of Vang, Fz and Dishevelled (Dsh), a membrane-associated protein acting downstream of Fz, in orienting SOP polarity.Genetic and live imaging analyses suggest that Dsh restricts the localization of a centrosome-attracting activity to the anterior cortex and that Vang is a target of Dsh in this process.Additionally, we find that the activity of Vang is dispensable for the non-autonomous polarizing activity of fz.

ABSTRACTDrosophila sensory organ precursor cells (SOPs) divide asymmetrically along the anterior-posterior (a-p) body axis to generate two different daughter cells. Planar Cell Polarity (PCP) regulates the a-p orientation of the SOP division. The localization of the PCP proteins Van Gogh (Vang) and Frizzled (Fz) define anterior and posterior apical membrane domains prior to SOP division. Here, we investigate the relative contributions of Vang, Fz and Dishevelled (Dsh), a membrane-associated protein acting downstream of Fz, in orienting SOP polarity. Genetic and live imaging analyses suggest that Dsh restricts the localization of a centrosome-attracting activity to the anterior cortex and that Vang is a target of Dsh in this process. Using a clone border assay, we provide evidence that the Vang and fz genes act redundantly in SOPs to orient its polarity axis in response to extrinsic local PCP cues. Additionally, we find that the activity of Vang is dispensable for the non-autonomous polarizing activity of fz. These observations indicate that both Vang and Fz act as cues for downstream effectors orienting the planar polarity axis of dividing SOPs.